Thermoplastic polyesters, e.g. polyalkylene terephthalates, have superior moldability, mechanical properties, heat stability, weather resistance, and electrical insulating properties, hence being used in extensive areas including those of electrical or electronic parts, automotive parts, etc. However, the application of thermoplastic polyesters are considerably restricted because of the low stiffness at elevated temperatures and the low impact resistance, particularly the inferior notched impact strength.
For instance, it has been investigated to make the most of superior mechanical and thermal properties of thermoplastic polyester resins in order to use them as materials for exterior panels of automobiles for on-line coating production, but such use has not been realized up to now on account of the insufficiency in stiffness at elevated temperatures and in impact resistance. In corporation of glass fiber, carbon fiber, wollastonite, or the like into thermoplastic polyester resins improves the high-temperature stiffness but has the drawback of lowering further the impact resistance and deteriorating the surface appearance. Blending of thermoplastic polyester resins with a rubber-reinforced resin improves the impact resistance but lowers the heat resistance represented by the high-temperature elastic modulus or the like; hence such blends are unfit for the on-line coating. In addition, since their linear expansion coefficients are large and their molded articles may show notable sink marks at the rib or boss portions, the blends cannot be applied as materials for exterior panels of automobiles. That's the present situations.
On the other hand, Japanese Patent Publication No. 51-21664 discloses that polyethylene terephthalate or polybutylene terephthalate is blended with a polyphenylene ether resin with the object of improving the moldability and processability thereof. However, this blending does not provide products much satisfactory in impact resistance.